Thermal conduction has long been a critical factor influencing the performance and development direction of electronic products. For example, the chip of a computer usually carries a great quantity of transistors. Under the tendency of fabricating slim and lightweight electronic products, more and more transistors are crowded into smaller and smaller space, which makes heat hard to dissipate. LED (Light Emitting Diode) has been extensively applied to illumination recently. LED emits light with a great amount of heat generated simultaneously. If heat cannot be removed effectively, the service life of LED will be obviously shortened. Therefore, thermal conduction performance would influence the development of high power LED.
There have been many techniques developed to overcome the abovementioned thermal conduction problems of electronic products. Diamond materials have the advantages of high thermal conductivity and low thermal expansion coefficient. Therefore, manufacturers have paid much attention to develop thermal conduction devices containing diamond material. For example, U.S. Pat. No. 6,987,318 disclosed a diamond composite heat spreader having thermal conductivity gradients and associated methods. The heat spreader consists of diamond particles and a braze alloy wrapping the diamond particles, wherein the varied diamond concentration generates thermal conductivity gradient, and wherein the area near the heat source has higher thermal conductivity. Thereby, the consumption of diamond particles is reduced. In fabrication, diamond particles having different particle sizes are sequentially arranged in a mold, and an interstitial material is filled into the gaps. Then, the interstitial material and the diamond particles are integrated via sintering, diffusion or electrodeposition.
US patent publication No. US 2005/0189647 disclosed a carbonaceous composite heat spreader and associated methods, wherein graphite and diamond particles are distributed in an aluminum matrix. Graphite can increase isotropy of thermal conduction in the spreader. In fabrication, a graphite layer is placed in a mold, and then a layer of diamond grits is stacked over the graphite layer. The layer of diamond grits is formed via bonding diamond particles with a binder. The stacking of a graphite layer and the c is repeated several times. Then, molten aluminum or molten aluminum alloy is poured into the mold. After solidification, the heat spreader is obtained.
In U.S. Pat. No. 6,987,318, diamond particles are stacked in a three-dimensional structure beforehand. Next, the three-dimensional structure is placed in a mold, and the interstitial material is filled into the voids. However, the filling of the interstitial material is likely to alter the three-dimensional arrangement of diamond particles. Thus, performance of the heat spreader usually deviates from expectation. Besides, there is difference between the thermal expansion coefficients of the diamond particles and the filling material, which impairs the fabrication of a large-area heat spreader. In US patent publication No. US 2005/0189647, graphite layers and layers of diamond grits also need stacking in a three-dimensional structure in advance. Therefore, the same problem also occurs.